Friends is getting a raw deal here - yes it can get schmaltzy but that's not all it is. The first few seasons in particular were full of witty scripting and some terrific performances. Even most of the schmaltzy bits are usually immediately balanced by a sucker punch of some kind. It did out-stay its welcome, it should have ended long before it did but it's misleading to dismiss it as a puke-fest or to continually condemn it as the uncool one next to Seinfeld and Sanders (both of which I absolutely love, esp. Sanders).
To answer the question: undoubtedly, in my mind, British. Yes there's some great US stuff out there and I love some of it but as maxi29 said, we get the very cream of the richest pickings. Bar a few rare examples US telly is absolutely shackled by its terror of the tyrannical networks, creating a bland unadventurous TV landscape consisting almost entirely of middle-ground. And PEPPERED with adverts. Tragically, some of the UK networks - E4 in particular - are starting to mimic the US habit of throwing in adverts straight after the opening titles. We used to get 2 ad breaks per hour - now we get 4 or 5, and I hate it.
British TV has almost always been the trailblazer, with the US hanging on to its coat-tails. Quatermass, The Wednesday Play, Til Death, Steptoe, the Dennis Potter plays, Horizon, costume drama, Edge of Darkness, The Singing Detective, Cracker, State of Play... no US network could have come up with anything remotely like any of those but they've copied some of them and countless others. Sometimes when I despair of British TV - and I regularly do - I have to remind myself it's still better than everywhere else.